Pressure tube and hand switch



Feb. 20, 1934. HENNlNG 1,948,175

PRESSURE TUBE AND HAND SWITCH Filed June 15, 1931 2 Sheets-Sheet 1 GURRENT SUPPLY Feb. 20, 1934. M. E. HENNING PRESSURE TUBE AND HAND SWITCH Filed June 15, 1931 2 Sheets-Sheet 2 Patented Feb. 20, 1934 PATENT OFFICE PRESSURE TUBE AND HAND SWITCH Malcolm E. Henning, Des Moines, Iowa, assignor to Penn Electric Switch 00., Des Moincs, Iowa,

a corporation of Iowa Application June 15, 1931.

2 Claims.

The object of my invention is to provide a pressure tube and hand switch which is simple, durable and comparatively inexpensive to manufacture.

A further object is to provide a switch structure in which an armature arm is pivotally mounted and its movements controlled by a pressure tube commonly known as a Bourdon tube, a magnet being associated with the armature arm for assisting in snap action of the switch structure, with switch contacts mounted in the magnetic field of the magnet whereby the arc produced between the contacts upon their separation is efiectively blown out by the magnetic current.

A further object is to provide a resilient connection between the Bourdon tube and the armature arm whereby to cause effective snap action of the switch structure.

Still a further object is to provide means for manually operating the switch structure in the event that it is not connected with pressure or the pressure is so low that it does not operate the switch, a spring being provided for hand operation, which is rendered ineffective when automatic operation is in process.

Still a further object is to provide the combination of a pressure tube and an armature arm for controlling switch contacts, with means for adjusting the position of the magnet relative to i the armature arm for thereby varying the differential of operation of the structure.

With these and other objects in view my invention consists in the construction, arrangement and combination of the various parts of my device, whereby the objects contemplated are attained, as hereinafter more fully set forth, pointed out in my claims, and illustrated in the accompanying drawings, in which:

Figure 1 is a perspective view of a pressure tube switch structure embodying my invention and showing it diagrammatically connected with a mechanical electrically operated refrigerator.

Figure 2 is a sectional view on the line 2-2 of Figure 1 showing the details of the pressure tube switch structure on an enlarged scale.

Figure 3 is a horizontal sectional view on the line 33 of Figure 2.

Figure 4 is a vertical sectional view on the line 44 of Figure 2; and

Figure 5 is a view of part of Figure 2, showing the device adjusted for hand operation.

The switch structure herein disclosed is adapted for both automatic operation (it being responsive to pressure variations) or hand operation.

Serial No. 544,558

The present invention contemplates the adaptation of a magnetic switch structure (such as shown in my co-pending application, Serial No. 423,677, filed January 27, 1930) for operation on higher pressures than are possible in connec tion with expansible bellows as shown in such application. I have shown a pressure or Bourdon tube operatively connected with the switch structure in the present application.

On the accompanying drawings, the reference 66 numeral 10 indicates a back wall of a casing A which has a peripheral wall 12. A cover plate is indicated at 14.

Within the casing A an entrance fitting 16 is provided having threads 18 with which piping or 7 copper tubing for conveying pressure to the fitting 16 may be connected. Extending from the fitting 16 is a pressure or Bourdon tube 20 terminating in a closed cap 22 provided with a perforated ear 24. Pivotally connected with the perforated ear 24 is an actuating rod 26 preferably of insulating material.

The switch mechanism of the structure includes a base 28 of insulating material, suitably secured to the casing A by screws 30, for instance. Terminal screws 32 and 34 extend from the base 28 through insulating bushings 36, which extend through the back 10 of the casing A. The terminal screw 32 secures a bracket 38 in position on the insulating base 28.

Pivoted on a pin 40 supported by the bracket 38, is an armature arm 42. The armature arm 42 has a stop lug 44 adapted to engage the bracket 38, to limit the movement of the armature arm in one direction. I

I provide an operative connection between the armature arm 42 and the actuating rod 26 in the form of a resilient leaf spring 46 and an adjusting screw 48. The adjusting screw 48 extends loosely through an opening adjacent the outer end of the leaf spring 46 and has a head 48a to engage therewith. The screw 48 is threaded into the actuating rod 26 and a locknut 50 is provided thereon for retaining the parts in any adjusted position desired.

Associated with the armature arm 42 and acting thereupon I provide a magnet 52. The magnet 52 is supported on, but insulated from a bracket 56. The bracket 56 is connected with the terminal screw 34. The bracket 56 includes upstanding side plates 56a between which a contact plate 58 is slidably mounted. The contact plate 58, the magnet 52 and the bracket 56 are retained against the insulating base 28 by a screw 60, a nut 62 and a spring 64 (see Figure 3).

The contact plate 58 carries a stationary contact 66. A movable contact 68 is carried by and movable with the armature arm 42. The contact 68 is of shouldered construction, as best shown in Figure 5 and is connected with the armature arm 42 by a leaf spring '70. The stationary contact 66 constitutes a stop for the armature arm 42 when the contacts are in engaged position as shown in Figure 2 and when the armature arm is adjacent the poles of the magnet 52.

The contact plate 58 is adjustable up and down (viewing it in the position shown in Fig. 2) by rotation of an adjusting sleeve '72 on the screw 60. The sleeve '72 has an eccentric portion 74 c0- acting with a transverse slot '76 of the contact plate 58 whereby to slide the plate as fully disclosed in my copending application hereinbefore referred to. Thus the stationary contact and stop 66 may be adjusted for stopping the armature arm 42 at diiierent distances from the poles of the magnet 52 and consequently in magnetic fields of different strengths, whereby to change the differential of operation of the device as hereinafter more fully described.

In connection with the armature arm 42, I provide a hand control rod 78, preferably of insulating material, which is connected therewith and extends through a slot 80 in the cover 14 of the casing A. For use with the armature arm when hand control is desired, I provide a spring 82 which is normally engaged with a pin 84 to render it ineffective, as shown in Figure 2, when automatic operation as controlled by the means of the Bourdon tube 20 is desired. The spring 82 can be disengaged from the pin 84 and engaged with the armature arm 42, as shown in Figure 5, when hand operation is desired.

Practical operation My pressure tube switch is especially designed for protection against excessively high pressures in the refrigeration systems of electric refrigerators on moving vehicles, such as railway trains, wherein it is undesirable to have switches such as those of the mercury tube type, which are affected by motions of the train. In such installations, the refrigerant used must be of non-harmful kind in the event of leakage. Carbon-dioxide, for instance, is desired as in the event of leakage, such as would be caused by wrecks or the like, the escape of the gas does not have an injurious effect upon the passengers of the train.

In using carbon-dioxide in a refrigerating system, however, it must be used under such high pressures as would cause bursting of an ordinary sylphon bellows and I have accordingly combined a high pressure or Bourdon tube with a magnet operating upon an armature arm in the present invention.

The device is shown connected diagrammatically with a refrige"ator in Figure l, with tubing 86 connected with the fitting l6 and with a refrigerator B. The tubing 86 is connected with the refri erant supply pipe 88.

The terminal screws 32 and 34 are connected in the circuit, of the electric motor 90 for the refrigerant compressor 92, whereby separation of the contacts and 68 will open the motor circuit in the case of an excessively high pressure being generated in the pipe 88 as caused by clogging of any part of the system.

For automatically controlling the motor 90, a temperature responsive control switch (not shown) is connected in the motor circuit in the ordinary manner, for instance, as shown in my copending application hereinbefore referred to. During normal operation, the contacts 66 and 68 are engaged with each other, with the head 48a of the adjusting screw 48 either touching the leaf spring 46 as shown in Figure 2, or spaced more or less therefrom. The head 48a will remain in substantially the same position during normal operation of the refrigeration system because of a predetermined high pressure at which the refrigerant is under when in the refrigeration system.

In the event excessively high pressure in the refrigerant pipe lines is built up, the pressure tube 20 will cause downward movement of the head 48a of the adjusting screw 48, first causing engagement of the head with the leaf spring 46 and then bending of the leaf spring to thus place it under tension and finally effect a separation of the contacts 66 and 68 by overcoming the magnetic pull on the armature arm 42. As soon as the armature arm starts to move away from the magnet, the stored energy in the leaf spring 46 quickens such movement and such movement is also quickened by reason of the fact that the armature arm during movement assumes new positions in continuously weakening fields of the magnet 52. After the armature arm has gained slight momentum, the contacts 66 and 68 are quickly separated and since they are located in the magnetic field, the magnetic current tends to extinguish the are formed between the contacts.

The armature arm is stopped in its opening movement by the stop lugs 44 engaging the bracket 38. When the Bourdon tube again assumes the position shown in Figure 2, due to a restoration of normal pressure in the refrigerant pipes, the contacts 66 and 68 will be allowed to be engaged by the pull of the magnet on the armature arm.

As stated before, the diiferential of operation of the switch structure may be varied by rotating the sleeve 72 and thus changing the magnetic field relative to the armature arm. The device can thus be set to open and close at relatively wide or narrow limits. The range of the device in its automatic operation can be adjusted by rotation of the screw 48 relative to the sleeve 26.

When the adjusting screw 48 assumes a position as shown in Figure 5, due to either no pressure in the tube 20 or normal pressure insuflicient to cause engagement of the head 48a with the spring 46, the switch structure can be opened and closed by hand engagement of the control rod for swinging the armature arm in either direction. In hand operation of the device, the spring 82 must be released from the pin 84 so as to cause engagement of the stop lugs in off position and prevent dropping of the armature arm against the stop contact 66, when it is desired to have the circuit broken. The spring 82, however. must be of insuiiicient tension to overcome the magnetic pull of the magnet 52 on the armature arm 42, when the contacts 66 and 68 are engaged so they will remain in such engaged position until manually disengaged.

Although I have shown the device in connec tion with a refrigerator, it is obvious that it can be used to control any other electric circuit, depending on pressure conditions. The hand operation of the device can be effected regardless of the circuit being controlled or the type of electric installation.

some changes may be made in the construction and arrangement of the parts of my device with out departing from the real spirit and purpose of my invention, and it is my intention to cover by my claims, any modified forms of structure or use of mechanical equivalents, which may be reasonably included within their scope.

I claim as my invention:

1. In a controller structure, a controller arm movable to two opposite positions, an actuating element normally engaging said controller arm, a magnet constraining said controller arm toward one of said positions and toward engagement with said actuating element, said controller arm being manually operable to either of its opposite positions when said actuating element is in nonnormal position spaced from said controller arm, means to maintain it in position spaced from said magnet comprising a spring constraining the controller arm toward position spaced from the magnet and of sufficient strength to maintain it in such position but insuificient to overcome the magnetic pull when the controller arm is in position adjacent said magnet and means to render said spring inoperative to affect the controller arm when the controller structure functions normally.

2. In a controller structure, a controller arm movable to two opposite positions, a magnet affecting said arm, actuating means for moving said arm toward position spaced from said magnet or permitting it to be attracted thereby to a position thereadjacent, said controller arm being manually operable to either of its opposite positions when said actuating element is in nonnormal position spaced from said controller arm, means to maintain it in position spaced from said magnet comprising a spring constraining the controller arm toward position spaced from the magnet and of sufiicient strength to maintain it in such position but insufficient to overcome the magnetic pull when the controller arm is in position adjacent said magnet and means to render said spring inoperative to afiect the controller arm when the controller structure functions normally.

MALCOLM E. I-IENNING. 

